Electrolytic process of making alkali perborates.



- mmmmm QTTO LIEBKINECET, F ERANKFOELT-ON-THE-MAIN, GERMANY, ASSIGNOR TO THE ROES SLER & HASSLACHER CHEMICAL (36., OF NEW YORK, N. Y., A CORPORATION or new roan.

ELECTROLYTIC PROCESS OF MAKING ALKALI PERBORATES.

No Drawing.

of sodium perborate by an electrolytic process,

Perbor'at-es .are usually manufactured by the well-known 'lanatar method wherein oxygen is transferred to borates from any substance carrying oxygen in available form; such substances are for instance, hy-

drogerrperoxid, sodium peroxid, and percarbonates of various origin.

The above substances, however, can only be obtained at high price, nor are the per borates obtainable therefrom. 3"OClL1ClblE at a sufficiently low price a. is desirable in view of their meritorious properties.

4 It has been tried for a long time to obtain the same result by the electrolytic oxidation of a solution of a hereto and to operate this process on a commercial scale by electrolyzing a mixed solution of an alkali borate and an alkali carbonate.

These efforts, however, met with considerable difficulties and a noteworthy success could not be achieved for the reason already recognized by Tanatar, who in Zcvltachm'ft fuc'r- Physikalische Uhemic, vol. 29, page 162, makes the following statement: The electrolytic current (electrolysis) also decomposes the perborates though the generation of small quantities of perborates is taking place during the electrolysis of concentrated solutions.

This important statement leaves no doubt that a considerable concentration of oxygen cannot be obtained by the electrolysis ot' a solution of borates, and that an equilibrium is reached very soon with a rather weak concentration of oxygen so that just as much perborate is decomposed as is generated.

I have now made the surprising observation that the'electrolytic production of alkali perbo'ates, as for instance of sodium Specification 01 Letters Eatent.

Fatented (lane a, 1918.

Application filed Qctober 23, 1915. Serial No. 57,398.

perbora'te, proceeds in a commercially successful manner if solid borax is present, preferably suspended, in the solution of alkali carbonate submitted to the action of the electric current, whereby unexpectedly, solid sodium perborate is directly obtained.

It I suspend for instance granulated borax,'in a. solution of soda, through which an electric current is passing, I succeed in a. short time in proving active oxygen to be present in the precipitate i. 0. sodium perborate has been generated. By duly continuing the electrolysis I succeed intransforming all the boraX into a marketable sodium perborate of crystallized form. I thus obtain marketable, solid sodium perborate immediately in one single operation.

My invention offers also the further ad vantage of making any desired mixture of perboratc and boraX (perbora-x) by discontinuing the electrolysis at a given moment.

The reaction can also be accelerated by adding to the solution, certain agents, as for instance, sodium perborate, to which also sodium bicarbonate, or materials generating such, may be added.

In further investigating the reaction, I found. it very much dependent upon the purity of the applied raw-materials. Impurities, often present in these materials, and known to be catalyzers, as for instance iron-compounds, disturb the generation of solid perborate very considerably. If '1 electrolyze solutions carrying such impurities, a de-poisoning or self-purification by the effect of the electrolysis takes place only after a certain time, whereupon the normal generation of perborate continues. To avoid this disadvantage entailing a loss of energy, I apply such raw materials as are practically free from catalyzers or I remove the catalyzers from the raw materials; to achieve this latter purpose it is sufficient for instance in the case of applying a solution of Solvay-soda, containing almost always a certain quantity of iron compounds even after filtration, to boil such solution and to known to be negative catalyzers exerting a protective action. The yields I obtain for instance with an "unpurified solution of Solvay-soda, to which I add small quantities of stannic acid, are equal to those obtained With a purified solution of soda; I am almost under the impression that these agents exert a protective action as well as a favorable efi'ect thus recommending their application also in the use of raw materials practically free from catalyzers. Sodium pcrborate or similar materials Work in the same direction, as their addition counteracts the effect of the catalyzers; The favorable efi ect of these agents is even enhanced by the presence of several of the same.

In the practical operation of my invention I have found that the density of current may vary Within a very great range; for instance I may work with a density of 2000 amp. per square meter as well as with one half or double this density; the temperature may likewise vary within a great range. However, I have found the temperature of 13 C.

very suitable for the process.

In using the expression granulated borax both in the specificationand claims, I mean to include borax sufficiently finely divided for the purpose in hand although in practice I prefer to use borax in such finely divided state that like. I I claim:

1. The process of making alkali perborates, consisting in electrolyzing a solution of an alkali carbonate in the presence of a solid alkali borate. p

2. The process of making alkali perborates, consisting in electrolyzing a solution of an alkali carbonate in the presence of a solid granulated alkali borate, said alkali borate being suspended in the solution of the alkali carbonate.

3. The process of making alkali perborates, consisting in rendering a solution of an alkali carbonate substantially free from catalyzing substances,- maintaining a solid anulated alkali borate free from catalyzing substances suspended in said solution and electrolyzing the solution containing the solid alkali borate in suspension.

4. The process of making alkali perborates, consisting in preparing a solution of it is substantially dustan alkali carbonate previously rendered free from catalyzers, maintaining a solid granu lated alkali borate previously rendered free from catalyzers suspended in said solution and electrolyzing the solution containing the solidalkali borate in suspension.

5. The process of making alkali perborates, consisting in preparing a'solution of an alkali carbonate, maintaining a solid granulated alkali borate suspended in said.

solution, adding to the mixture substances adapted to-counteract; the efiect of catalyzers recesses contained in aforesaid solution of alkali salts and electrclyzing the solution contain-v ratcs, consisting in preparing solution of an alkali carbonate, maintaining a solid granulated alkali borate suspended in said solution and electrolyzing the solution in the presence of a mixture of an alkali bicarbonate, an alkali perboratc and stannic acid to accelerate the reaction;

9. The process or" making alkali perborates, consisting in preparing a solution of alkali carbonate maintaining a solid granulated alkali borate suspended in said solution and electrclysing the solution in the presence of an alkali bicarbonate to accelerate the reaction.

10. The process of making alkali perborates, consisting in preparing a solution of alkali carbonate, maintaining a solid granulated alkali borate suspended in said solution and elcctrolyzing the solution in the presence of an alkali perborate to accelerate.

presence of a mixture of an alkali perborate and an alkali bicarbonate to accelerate the reaction.

12. The process of making alkali perberates, consisting'in preparing a solution of alkali carbonate, maintaining a solid granulated alkali borate suspended in said solution, counteracting the effect of catalyzing substances by adding stannic acid to. the mixture and then electrolyzing the letter.

13. The process of making sodium perborate, consisting in electrolyzing asolution of soda in the presence of solid boraX.

is. The process of making sodium perborate, consisting in electrolyzing a solution of soda in the presence at solid granulated borax, said granulated borax being suspended in the solution of the soda.

15. The recess ofniakin sodium erbomesses a stances, maintaining solid granulated borax free from catalyzing substances suspended in said solution and electrolyzing the solution containing the solid borax in suspenslon.

16. The process of making sodium perborate, consisting in preparing a solution of soda previously rendered free from catalyzers, maintaining solid'granulated borax previously rendered free from catalyzers suspended inlsaid solution and electrolyzing the solution containing the solid borax in suspension.

17. The process of making sodium perborate, consisting in'preparing a solution of soda, maintaining solid granulated borax suspended in said solution and electrolyzing the same in the presence of a mixture of sodium bicarbonate, sodium perborate and stannic acid to accelerate the reaction.

18. The process of making sodium perborate, eonsisting in preparing a solution of soda, maintaining solid granulated borax suspended in said solution, and counteracting the effect of catalyzers'by adding stannie acid to the mixture While electrolyzing the latter.

19. The process of making sodium perborate, consisting in preparing a solution of soda, maintaining solid granulated borax suspended in said solution and electrolyzing the solution in the presence of sodium bicarbonate to accelerate the reaction.

20. The process of making sodium perborate, consisting in preparing a solution of soda, maintaining solid granulated borax suspended in said solution and electrolyzing the solution in the presence of sodium perborate to accelerate the reaction.

21. The process of making sodium perborate, consisting in preparing a solution of soda, maintaining solid granulated borax suspended in said solution and electrolyzing the solution in the presence of a mixture of sodium bicarbonate and sodium perborate to accelerate the reaction.

In testimony Whereot'I have signed this specification in the presence of two subscribing witnesses.

OTTO LIEBKNEOHT.

lVitnesses JEAN GRUND, CARL Gnome. 

